the late tamerlan tsarnaev paid to dagestan in 2012. the parents are reportedly telling authorities that no contact was made between him and radical islamist there is. a group is claiming the same thing. there are a lot of questions about that trip. different reasons for him going. conflicting timelines where he was, who he was with. a lot of focus on one mosque in dagestan tamerlan said to have attended during the trip and a prior one. it is a salafist mosque, a extreme mosque one which radicals have attended. there is one report russian officials think he did make contact several times with an extremist, bill. bill: greg, we don't know when this man turned, whether it was in the u.s. in boston or whether it was overseas. what is the working theory on behalf of authorities when tamerlan, the older brother, could have been radicalized? >> reporter: very good question. it is always a possibility that the turning happened exactly there in that country but in fact he was, we believe, closely watched. our own amy kellogg here speaking to a